1. Field of the Invention
The present invention relates generally to chemical mechanical polishing (CMP) top pole fabrication techniques, and more particularly to a method for forming a write head top pole using chemical mechanical polishing with a diamond-like-carbon (DLC) polishing stop layer.
2. Description of Related Art
Fixed magnetic storage systems are now commonplace as a main non-volatile storage in modern personal computers, workstations, and portable computers. Storage systems are now capable of storing gigabyte quantities of digital data, even when implemented in portable computers.
As disk drive technology progresses, more data is compressed into smaller areas. Increasing data density is dependent upon read/write heads fabricated with smaller geometries capable of magnetizing or sensing the magnetization of correspondingly smaller areas on the magnetic disk. The advance in magnetic head technology has led to heads fabricated using processes similar to those used in the manufacture of semiconductor devices.
A typical disk drive is comprised of a magnetic recording medium in the form of a disk for storing information, and a magnetic read/write head for reading or writing information on the disk. The disk rotates on a spindle controlled by a drive motor and the magnetic read/write head is attached to a slider supported above the disk by an actuator arm. When the disk rotates at high speed, a cushion of moving air is formed lifting the air bearing surface (ABS) of the magnetic read/write head above the surface of the disk.
The read portion of the head is typically formed using a magnetoresistive (MR) element. This element is a layered structure with one or more layers of material exhibiting the magnetoresistive effect. The resistance of a magnetoresistive element changes when the element is in the presence of a magnetic field. Data bits are stored on the disk as small, magnetized regions on the disk. As the disk passes by beneath the surface of the magnetoresistive material in the read head, the resistance of the material changes and this change is sensed by the disk drive control circuitry.
The write portion of a read/write head is typically fabricated using a coil embedded in an insulator between a top and bottom magnetic layer. The magnetic layers are arranged as a magnetic circuit, with pole tips forming a magnetic gap at the air bearing surface of the head. When a data bit is to be written to the disk, the disk drive circuitry sends current through the coil creating a magnetic flux. The magnetic layers provide a path for the flux and a magnetic field generated at the pole tips magnetizes a small portion of the magnetic disk, thereby storing a data bit on the disk.
A thin film write head comprises two pole pieces, a top pole P2 and a bottom pole P1. A write head generally has two regions, denoted a pole tip region and a back region. The pole pieces are formed from thin magnetic material films and converge in the pole tip region at a magnetic recording gap, known as the zero throat level, and in the back region at a back gap. The zero throat level delineates the pole tip region and back region. A write head also has pole tip thickness, P1T and P2T, associated with, and extensions of P1 and P2 respectively.
In current magnetic head writer fabrication, P2 is formatted by plating through a photoresist trench, ion milling to a desired write width, filling with alumina, and then planarizing the surface by chemical mechanical polishing (CMP), thereby opening P2 (for connecting to yoke P3). In traditional magnetic head fabrication, the thickness variation sigma from both P2 plating and CMP is such that 0.8 um P2T has to be consumed by CMP to allow opening of all P2. In order to achieve this, an extra 0.8 um of material must be plated over final P2T target of P2, which in turn requires the photoresist thickness to be increased to meet the P2T target. However, increasing the photoresist thickness and trench aspect ratio reduces the photo resolution and the photo process window, thereby resulting in a larger P2 critical dimension sigma. In pole photo processes, such as deep ultraviolet (DUV) photo processes, this high P2T poses further challenges due to its smaller depth of focus compared with lithography exposure tools using I-line wavelength photo processes.
It can be seen then that there is a need for a new method for forming a write head top pole using chemical mechanical polishing with a stop layer.